Op jonge leeftijd meer ultraviolet licht, later minder kans op MS

Multiple sclerosis (MS) is a chronic disease in which the immune system mistakenly attacks and breaks down the nerves, causing patients to gradually experience increasing symptoms of loss of function and paralysis. There are still no medicines to treat MS, but it is becoming increasingly apparent that people who have been exposed to relatively high levels of sunlight on their skin during childhood are less likely to develop MS. According to a recent Australian study published in Neurology, this also applies to the variants of MS that affect children and teenagers.

MS usually starts somewhere between the ages of 20 and 50, but in about 5 per cent of all patients, the disease appears before they reach the age of 18. A group of Australian scientists and doctors studied 332 study participants aged 4-22 who had been diagnosed with MS before the age of 18 and compared them with 534 study participants of the same age who were healthy.

The Australians asked the study participants how often they were outside in the summer. They discovered that being outside in the summer seemed to offer protection against MS. Children and teenagers who spent half an hour outside every day in the summer were 50 per cent less likely to develop MS than the study participants who were outside less often. Children and teenagers who spent 1 to 2 hours outside every day were even better protected. Compared to those who stayed indoors, they were 78 percent less likely to develop MS.

It was already known that exposure to sunlight protects against MS in general, and that children who grow up in a country or region where the sun shines often are less likely to develop MS later in life. An obvious explanation for the protective effect of sunlight is vitamin D. After all, ultraviolet light that falls on uncovered skin is the most important source of vitamin D.

But although research shows that high vitamin D levels do indeed protect against MS, that may not be the whole story. In the Australian study, the researchers found no link between MS and vitamin D levels. The same is true of a study published in 2018, in which American neurologists compared people of European, Latin and African ethnicity.

In people of European descent, both exposure to sunlight and high vitamin D levels reduced the risk of MS. In study participants of Latin American and African descent, the researchers found no protective effect of vitamin D levels. However, in these groups, exposure to ultraviolet light did reduce the risk of MS. Perhaps ultraviolet light has more positive effects than just increasing vitamin D levels.